nodeJS与MySQL实现分页数据以及倒序数据

// 数据库信息
var connection = mysql.createConnection({
 host   : 'localhost',
 port:3306,
 user   : 'root',
 password : '',
 database : 'url',
 multipleStatements: true //这里一定要加上这个。先别管什么用，一定要加上。
});

// 获取url
router.post('/csdnurl', async (ctx, next) => {
  var start = (ctx.request.body.page - 1) * 10;
  var sql = 'SELECT COUNT(*) FROM csdnurl ORDER BY id DESC; SELECT * FROM csdnurl ORDER BY id DESC limit ' + start + ',10';
  let results = await query2(sql);
  ctx.body = results
});

const query2 = function (sql) {
  return new Promise((resolve, reject) => {
    connection.query(sql, function (error, results) {
      if (error) {
        reject(error);
      } else {
         var allCount = results[0][0]['COUNT(*)'];
         var allPage = parseInt(allCount) / 10;
         var pageStr = allPage.toString();
         if (pageStr.indexOf('.') > 0) {
           allPage = parseInt(pageStr.split('.')[0]) + 1;
           console.log(allPage)
         }
         var List = results[1];
        resolve(List)
      }
    });
  })

var Koa = require('koa');
var Router = require('koa-router' );
var bodyParser = require('koa-bodyparser');
var mysql = require('mysql');
var app = new Koa();
var router = new Router();
app.use(bodyParser());

var connection = mysql.createConnection({
 host   : 'localhost',
 port:3306,
 user   : 'root',
 password : 'xxx',
 database : 'url'
});
connection.connect();


//第一类封装 ，一般用于不传递多个参数
const query = function (sql) {
  return new Promise((resolve, reject) => {
    connection.query(sql, function (error, results) {
      if(error){
        reject(error);
      }else{
        resolve(results)
      }
    });
  })
}
//第二类封装 ，一般用于传递多个参数
const query1 = function (userStr,name,passwd,token1) {
  return new Promise((resolve, reject) => {
    connection.query(userStr, function (error, result) {
      if(error){
        reject(error);
      }else{
        if (result.length > 0) {
          json['message'] = '用户已经存在';
          json['resultCode']= 1;
        } else {
          json['message'] = '注册成功';
          json['token'] = token1;
          json['resultCode'] = 200;
          var insertStr = `insert into login (username, password,token) values ("${name}", "${passwd}","${token1}")`;
          console.log(insertStr)
          connection.query(insertStr, function (err, res) {
            if (err) throw err;
          })
        }
        resolve(json)
      }
    });
  })
}


// 使用第一类封装
router.get( '/csdnurl', async(ctx, next) => {
 var sql = "select * from csdnurl";
  let results = await query(sql);
  ctx.body=results
});
// 使用第一类封装
router.post('/login', async (ctx, next) => {
  var name = ctx.request.body.username;
  var passwd = ctx.request.body.password;
  var userStr = `select username,password,token from login where username="${name}" and password="${passwd}"`;
  let results = await query(userStr);
  ctx.body = results
});

// 使用第二类封装
router.post('/register', async (ctx, next) => {
  var name = ctx.request.body.username;
  var passwd = ctx.request.body.password;
  var token1 = jwt.sign({
    username: name
  }, secretkey, {
    expiresIn: 60 * 8
  });
  var userStr = `select * from login where username="${name}"`;
  let results = await query1(userStr,name,passwd,token1);
  ctx.body = json
});